1. Field of the Invention
The invention is related to detection of ionizing radiation (alpha, beta, gamma and neutron), chemicals, and other environmental threats, and more particularly, to a distributed system using multiple detectors arranged into self-organizing clusters, and connected using wired and wireless networks.
2. Description of the Related Art
There are a number of possible threats that law enforcement agencies need to be concerned about. These include threats from radioactive and nuclear materials, chemicals (whether released deliberately or accidentally into the environment, particularly into the atmosphere, including both industrial chemical releases and weaponized chemical releases), biological and bacteriological threats, and so forth. The general trend in such detection systems has been in reducing size and weight of individual detectors, and in making them generally more mobile and less expensive. However, a number of issues remain that need to be addressed in the field of radiation and chemical environmental threat detection. One of the problems, particularly in the field of radiation detection, is impracticality of reducing the size of the device below a certain form factor as this decreases sensitivity and hence effectiveness of detection. As one example, radiation detectors use a scintillation crystal or scintillation method to detect radiation. Scintillation method uses a crystal and a photo detector adjacent to the crystal, where events due to radiation interacting with the crystal are detected. The events are then processed, typically by some sort of a CPU, to generate an alarm and identify the nature of the detected radiation.
A practical reality of such radiation detectors is that the size of the interacting element (scintillation crystal, semiconductor, Geiger-Muller counter, ionization chamber, etc.) used to register the radiation event cannot be made much smaller than a certain size without creating difficulties in distinguishing background radiation from actual events. It should also be remembered that detection of radiation using a scintillation crystal (for example) is generally a probabilistic process—some number of events are detected per unit time, and a probabilistic model is used to filter out “real” events (signal) from background radiation (noise) and radiation from natural isotopes (false positives). Special algorithms must be used in the processing logic and software to filter out the false detection events.
However, when making the scintillation crystal smaller and smaller, it becomes more and more difficult to separate the false positive events (e.g. events caused by medical or naturally occurring isotopes) and background radiation from events caused by actual radiation and nuclear sources. This is generally the reason why a compromise must be found between sensitivity and accuracy of detection on the one hand, and device size and miniaturization concerns on the other. Although various methods for using statistical algorithms to “tease out” more data from smaller crystals (and smaller detection elements generally) are known, there are practical physical limits beyond which is it is impossible to improve sensitivity of the individual detectors by improving the data processing algorithms. These limits are based, at least in part, on the amount of data that is collected for statistical processing, below a certain threshold, more data will need to be collected per unit time, in order to provide sufficient data for the statistical analysis.
Another problem in the field of radiation detection is the difficulty in establishing directionality of the source of the signal by small mobile instruments—typically, personal radiation detectors (PRDs) do not have a mechanism for determining direction to the source of the radiation, and/or triangulation of the source, etc. Therefore, for a typical user, it is necessary to walk around with the detection device, looking for localized signal maxima. This process can be generally time consuming, often expensive and cumbersome. Also, it is desirable to avoid having to train users in the use of radiation detection devices.
Accordingly, there is a need in the art for a system and method that addresses the above problems.